Fiber optic telecommunications technology is becoming more prevalent as service providers strive to deliver higher bandwidth communication capabilities to customers/subscribers. The phrase “fiber to the x” (FTTX) generically refers to any network architecture that uses optical fiber in place of copper within a local distribution area. Example FTTX networks include fiber-to-the-node (FTTN) networks, fiber-to-the-curb (FTTC) networks, and fiber-to-the-premises (FTTP) networks.
FTTN and FTTC networks use fiber optic cables that are run from a service provider's central office to a cabinet serving a neighborhood. Subscribers connect to the cabinet using traditional copper cable technology, such as coaxial cable or twisted pair wiring. The difference between an FTTN network and an FTTC network relates to the area served by the cabinet. Typically, FTTC networks have cabinets closer to the subscribers that serve a smaller subscriber area than the cabinets of FTTN networks.
In an FTTP network, fiber optic cables are run from a service provider's central office all the way to the subscribers' premises. Example FTTP networks include fiber-to-the-home (FTTH) networks and fiber-to-the-building (FTTB) networks. In an FTTB network, optical fiber is routed from the central office over an optical distribution network to an optical network terminal (ONT) located in or on a building. The ONT typically includes active components that convert the optical signals into electrical signals. The electrical signals are typically routed from the ONT to the subscriber's residence or office space using traditional copper cable technology. In an FTTH network, fiber optic cable is run from the service provider's central office to an ONT located at the subscriber's residence or office space. Once again, at the ONT, optical signals are typically converted into an electrical signal for use with each subscriber's devices. Of course, to the extent that subscribers have devices that are compatible with optical signals, conversion of the optical signal to an electrical signal may not be necessary.
FTTP networks include active optical networks and passive optical networks. Active optical networks use electrically powered equipment (e.g., a switch, a router, a multiplexer, or other equipment) to distribute signals and to provide signal buffering. Passive optical networks use passive beam splitters instead of electrically powered equipment to split optical signals. In a passive optical network, ONT's are typically equipped with equipment (e.g., wave-division multiplexing and time-division multiplexing equipment) that prevents incoming and outgoing signals from colliding and that filters out signals intended for other subscribers.
FIG. 1 illustrates a FTTP network 100 deploying passive fiber optic lines. As shown, the network 100 can include a central office 101 that connects a number of end subscribers 105 in a network. The central office 101 can additionally connect to a larger network, such as the Internet (not shown) and a public switched telephone network (PSTN). The various lines of the network 100 can be aerial or housed within underground conduits.
The network 100 also can include fiber distribution hubs (FDHs) 103 having one or more optical splitters (e.g., 1-to-8 splitters, 1-to-16 splitters, or 1-to-32 splitters) that generate a number of distribution fibers that may lead to the premises of an end user 105. In typical applications, an optical splitter is provided prepackaged in an optical splitter module housing and provided with a splitter output in pigtails that extend from the module. The splitter output pigtails are typically connectorized with, for example, SC, LC, or LX.5 connectors. The optical splitter module provides protective packaging for the optical splitter components in the housing and thus provides for easy handling for otherwise fragile splitter components. This modular approach allows optical splitter modules to be added incrementally to FDHs 103 as required.
The portion of the network 100 that is closest to central office 101 is generally referred to as the F1 region, where F1 is the “feeder fiber” from the central office 101. The portion of the network 100 closest to the end users 105 can be referred to as an F2 portion of network 100. The F2 portion of the network 100 includes distribution cables routed from the FDH 103 to subscriber locations 105. For example, the distribution cables can include break-out locations 102 at which branch cables are separated out from the main distribution lines. Branch cables are often connected to drop terminals 104 that include connector interfaces for facilitating coupling of the fibers of the branch cables to a plurality of different subscriber locations 105 (e.g., homes, businesses, or buildings). For example, fiber optic drop cables can be routed directly from a breakout location 102 on the distribution cable to an ONT at a subscriber location 105. Alternatively, a stub cable can be routed from a breakout location of the distribution cable to a drop terminal 104. Drop cables can be run from the drop terminal 104 to ONT's located at premises 105 located near the drop terminal 104.
Distributed Antenna Systems (DAS) also are becoming more prevalent. DAS are used to provide wireless service (e.g., cell phone, WIFI, etc.) within a given geographic area. DAS include a network of spaced-apart antenna nodes optically or electrically connected to a common control location (e.g., a base station). Each antenna node typically includes an antenna and a remote unit (i.e., a radio head, a remote transceiver, etc.).
DAS enable a wireless cellular service provider to improve the coverage provided by a given base station or group of base stations. In DAS, radio frequency (RF) signals are communicated between a host unit and one or more remote units. The host unit can be communicatively coupled to one or more base stations directly by connecting the host unit to the base station using, for example, electrical or fiber telecommunications cabling. The host unit can also be communicatively coupled to one or more base stations wirelessly, for example, using a donor antenna and a bi-directional amplifier (BDA). One or more intermediate devices (also referred to here as “expansion hubs” or “expansion units”) can be placed between the host unit and the remote units in order to increase the number of remote units that a single host unit can feed and/or to increase the hub-unit-to-remote-unit distance.
RF signals transmitted from the base station (also referred to here as “downlink RF signals”) are received at the host unit. The host unit uses the downlink RF signals to generate a downlink transport signal that is distributed to one or more of the remote units. Each such remote unit receives the downlink transport signal and reconstructs the downlink RF signals based on the downlink transport signal and causes the reconstructed downlink RF signals to be radiated from at least one antenna coupled to or included in that remote unit.
A similar process is performed in the uplink direction. RF signals transmitted from mobile units (also referred to here as “uplink RF signals”) are received at each remote unit. Each remote unit uses the uplink RF signals to generate an uplink transport signal that is transmitted from the remote unit to the host unit. The host unit receives and combines the uplink transport signals transmitted from the remote units. The host unit reconstructs the uplink RF signals received at the remote units and communicates the reconstructed uplink RF signals to the base station. In this way, the coverage of the base station can be expanded using the DAS.
One general type of DAS is configured to use optical fibers to communicatively couple the host unit to the remote units and/or expansions hubs. However, such a fiber-optic DAS typically makes use of dedicated optical fibers that are deployed specifically to support that DAS.